caif: Add missing braces to multiline if in cfctrl_linkup_request

The indentation here implies this was meant to be a multi-line if.

Introduced several years back in commit c85c2951


("caif: Handle dev_queue_xmit errors.")

Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: David S. Miller <davem@davemloft.net>